1. Field of the Invention
The present invention relates to an interval photographing device for releasing the camera shutter at a certain predetermined time interval.
2. Description of the Prior Arts
Until now, the interval photographing device has been contributing much to the unattended photography for scientific studies, etc. which continue for several days in the place where no commercial current source is available. Where the interval photographing device is used, even if the object brightness is changed somewhat in the interval a proper exposure can be obtained with an automatic exposure mechanism built in the camera. However, when the object brightness is remarkably low, for example, in the night, outside the range of the automatic exposure of the camera, an electronic exposure device is required. Thus, when the interval photographing device is used together with the electronic flash device, it is an important consideration to save the power consumption so as to prolong the life of the battery.
Until now, as is disclosed in Japanese Patent Application Laid-Open No. Sho 53-116148, a preliminary signal is delivered to an electronic flash device before the start of the photographing so as to start the charge operation of the electronic flash device, whereby the power source switch of the electronic flash device is opened until a preliminary signal is delivered in order to avoid the power consumption. In this system, before photographing the preliminary signal is delivered to the electronic flash device so as to carry out the charge operation so that even when the object brightness is so high that the flash light is not necessary, the device emits the flash and, therefore, thus causing possibilities of an over exposure and a large power consumption. Therefore, the system is not suited for the object whose brightness changes.
Although quite recently, an electronic flash device which does not operate according to the object brightness has been proposed, the device is unavoidably charged, and a considerable power is consumed thereby so that the system is not suited for the interval photographing device with a battery.
In the case of the above interval photographing device, as the release signal is simply delivered at a certain predetermined interval and the shutter is released simply in accordance with the signal, it is necessary to always supply current to the light measuring circuit of the camera irrespectively of the release interval, so that even in the light measuring circuit the power is consumed in a disadvantageous way.